Buckle

ABSTRACT

A buckle ( 2 ) comprising a buckle body ( 4 ) with spaced apart side walls ( 6, 8 ) and a handle ( 10 ), the handle comprising a cam member ( 24 ) and being pivotally mounted between the side walls ( 6, 8 ) such that it is movable between an open position, wherein a strap ( 30 ) may be threaded upon the handle ( 10 ), and a closed position, wherein tension is applied to a strap ( 30 ) threaded upon the handle ( 10 ), characterised in that the buckle ( 2 ) further comprises strap trapping means ( 26, 28 ) arranged such that when the handle is in the closed position the strap trapping means ( 26, 28 ) defines a channel for the strap ( 30 ) threaded upon the handle, to prevent or reduce slippage thereof.

The present invention relates to a buckle.

Buckles have been used for a long time as tensioning and length adjusting devices, in particular in the aviation and road transport industries. For example, they have been used in conjunction with straps for securing a load or securing sheeting which is used to cover a load. Conventional buckles have a handle over which a strap is threaded, the handle being movable in an over centre manner to tension and secure the strap. Such buckles are generally known as over-centre buckles. The handle in an over-centre buckle is movable from an open position, in which a strap may be threaded onto the handle, to a closed position, in which the strap is secured under tension. The handles are generally provided with a locking mechanism for securing the handle in the closed position during use.

The present inventors have identified a problem with the conventional buckle design, namely that the buckle tends to allow the strap to slip when it is subjected to repetitive high frequency (e.g. 1 Hz), low force cyclic loads (e.g. gust loads experienced in aviation). This is thought to be due to the fact that when the tension is reduced the strap, which tends to be quite stiff, pushes through the buckle and loosens around the handle. When the tension is then reapplied this causes the strap to slip by a small amount. Through repeated cycles of loosening and tensioning the amount of strap slippage accumulates until the increase in strap length becomes quite noticeable and potentially dangerous.

It is the object of the present invention to overcome the limitations of the prior art, or at least to provide an alternative buckle to those currently available.

According to the present invention there is provided a buckle comprising a buckle body with spaced apart side walls and a handle, the handle comprising a cam member and being pivotally mounted between the side walls such that it is movable between an open position, wherein a strap may be threaded upon the handle, and a closed position, wherein tension is applied to a strap threaded upon the handle, characterised in that the buckle further comprises strap trapping means arranged such that when the handle is in the closed position the strap trapping means defines a channel for the strap threaded upon the handle, to prevent or reduce slippage thereof.

The term “strap”, as used herein, is a general term which is intended to cover strap, rope, webbing, cable and any other term which may be used to describe a length of material which may be used in conjunction with a buckle as described. The strap may be of any suitable material including, but not limited to, natural materials and plastics materials.

The handle may conveniently be mounted on a pin which extends between the side walls and about which the handle pivots. The cam member is provided on the handle and moves about the pin when the handle is pivoted. In use of the buckle the strap is threaded around the pin. When the handle is in the open position the cam member is held away from the strap and it then moves into contact with the strap when the handle is moved to the closed position to engage the strap and hold it under tension.

The strap trapping member is provided on the buckle and defines a channel for the strap when the handle is in the closed position. This serves to prevent, or at least reduce, any slippage of the strap through the buckle during use.

In an embodiment of the invention the buckle may be provided with more than one strap trapping means. This can serve to increase the efficiency of the buckle in preventing, or reducing, strap slippage.

In an embodiment of the invention the strap trapping means may define a channel for the strap which is the same width as, or slightly wider than, the thickness of the strap passing through the channel. The “width” of the channel is defined as the size of the gap created by the strap trapping means, through which the strap passes. It is believed that by providing a narrow channel which is the same width or only slightly wider than the thickness of the strap that slippage can be prevented or reduced. This is believed to be due to the fact that the channel restricts movement of the strap which can be caused by the high frequency, low force cyclic loads. The cyclic loads cause the strap to be repeatedly stretched and compressed along its length and this can gradually cause the strap to slip through the buckle over time. This is particularly true when the strap is made from a textile webbing. When a textile webbing strap is compressed along its length the individual textile strands “balloon” out of the plane of the strap. The size of the channel defined by the strap trapping means closely corresponds to the thickness of the strap and this prevents this “ballooning” and thus helps to prevent or reduce slippage. The strap trapping means does not compress the strap, but provides a closely profiled channel which restricts unwanted movement of the strap.

As will be seen in FIG. 4, the strap in an over-centre buckle is typically fed into the buckle, wound around a pin and fed back out of the buckle. This means that the strap in the buckle is generally present as a double layer of strap material. As a consequence of the double thickness of strap material the channel will typically be the same width as, or slightly larger than a double thickness of strap material. In instances where the strap is only present as a single layer of material then clearly the width of the channel will be reduced accordingly.

The function of the strap trapping means is to profile the strap and prevent it from moving out of plane, i.e. by “ballooning”, rather than to compress it. The terms “profile” and “profiled”, as used herein, mean that the width of the channel closely corresponds to the thickness of the strap, such that the strap cannot move out of plane, i.e. by “ballooning”. The channel does not compress the strap. The present inventors have discovered problems with buckles which compress straps, such as difficulty in closing buckles, problems with variances in strap width and instances of buckles coming open during loading. It is believed that at least some of these problems can be alleviated by channeling the strap rather than compressing it.

In an embodiment of the invention the strap trapping means may comprise a strap trapping member which is associated with the cam member, such that when the handle is moved from the open position to the closed position the cam member moves into close proximity with the strap trapping member. The distance between the strap trapping member and the cam member, when the handle is in the closed position, is defined as the width of the channel. The term “into close proximity” refers to a position relative to the strap trapping member which is sufficient to define a suitable channel for the strap. This position will vary depending on the size of the buckle and the thickness of the strap used, but the distance between the cam member and the strap trapping member when the handle is in the closed position will typically be approximately equal to, or slightly larger than, the thickness of a double layer of the strap in its normal, relaxed state. This will ensure that the strap is channeled between the cam member and the strap trapping member when the handle is in the closed position to prevent “ballooning” of the strap or other movement out of the plane of the strap, which may cause slippage of the strap.

In an embodiment of the invention the strap trapping member may be in the form of a plate. The plate may conveniently extend upwardly from the base of the buckle. The plate will only be supported at one end and will act as a simple spring. In an embodiment of the invention the plate may be orientated perpendicular to the side walls.

In an embodiment of the invention the plate may be angled towards the cam member. This improves the ability of the plate and the cam member to “trap” the strap. The plate may conveniently be angled from between 45□ to 90□ relative to a plane defined by the base of the buckle body. More preferably, the plate may be angled from 60□ to 80□ relative to the plane defined by the base of the buckle body. Most preferably, the plate may be angled at approximately 75□ relative to the plane defined by the base of the buckle body. The angle of the plate relative to the buckle body will be discussed in more detail with reference to the FIGS. 3 and 4.

In an embodiment of the invention the strap trapping member may have a roughened surface to increase friction between itself and the strap when the buckle is in the closed position. The surface of the strap trapping member may be knurled, toothed or provided with any other surface features which serve to increase friction between the strap trapping member and the strap and prevent the strap from slipping.

In an embodiment of the invention the strap trapping means may comprise mating members, a first member being provided on the handle and a second member being provided on the buckle body, the arrangement being such that when the handle is moved from the open position to the closed position the mating members come together. When the mating members come together they define a gap which is approximately equal to, or slightly larger than, the thickness of a double layer of the strap in its normal, relaxed state. This ensures that the mating members come together to define a channel for the strap when the handle is in the closed position. The channel profiles the strap to prevent “ballooning” of the strap or other movement which may cause slippage of the strap. The gap formed between the mating members is referred to as the width of the channel.

In an embodiment of the invention the mating members are in the form of plates. This increases the surface area which comes into contact with the strap and as a result improves the performance of the buckle in preventing, or reducing, slippage.

In an embodiment of the invention one or both of the mating members may have a roughened surface to increase friction between itself and the strap when the buckle is in the closed position. The surface of the mating member may be knurled, toothed or provided with any other surface features which serve to increase friction between the mating member and the strap and prevent the strap from slipping.

For a better understanding of the present invention reference will now be made, by way of example, to the accompanying drawings, in which:

FIG. 1 is a perspective view of a buckle according to the present invention in an open position;

FIG. 2 is a top view of the buckle of the buckle of FIG. 1 in a closed position;

FIG. 3 is a side sectional view of the buckle of FIG. 2 taken along line X-X; and

FIG. 4 shows the same view as FIG. 3 with the inclusion of a strap wound around the buckle.

Referring firstly to FIG. 1, this shows a buckle 2 of the type which may be used as a tensioning or length adjustment device for securing strapping, for example in the aviation and road transport industries. The buckle 2 is not limited to use in those industries and can be used in almost any situation where it is necessary to secure a length of material under tension, for example for securing a load or securing a curtain. The buckle 2 has a buckle body 4, a base 5 and two opposing side walls 6, 8 such that the buckle body 4 defines a generally U-shaped channel. The side walls 6, 8 are spaced apart by a distance which is slightly larger than the width of a strap (not shown) which the buckle 2 will be used to secure, such that the strap can lie along the base 5 of the buckle 2 between the two side walls 6, 8.

The buckle 2 comprises a handle 10 which is pivotally mounted on the buckle body 4 by a pin 12 which extends through the side walls 6, 8 and through corresponding apertures in the legs 9, 11 of the handle 10. The handle 10 is movable from an open position, as shown in FIG. 1, to a closed position, as shown in FIGS. 2-4. In moving from the open position to the closed position the handle 10 is pivoted about the pin 12 in a clockwise direction (relative to the view shown in FIG. 1). The handle 10 is provided with a spring biased latch 14 which functions as a locking mechanism to secure the handle 10 in the closed position during use. The side walls 6, 8 are provided with angled portions 16, 18 where the height of the side walls 6, 8 gradually decreases. The angled portions 16, 18 are associated with recesses 20, 22 such that when the handle 10 is moved from the open position to the closed position the spring biased latch 14, which is biased into a first position by a spring (not shown), comes into contact with the angled portions 16, 18 of the side walls 6, 8 and is deflected into a second position, whereby it bypasses the angled portions 16, 18 of the side walls 6, 8 and is received in the recesses 20, 22. When the spring biased latch 14 is received in the recesses 20, 22 the buckle 2 is effectively “locked” in the closed position until a force is applied to the spring biased latch 14 to overcome the biasing force of the spring and release the latch 14 from the recesses 20, 22.

The handle 10 further comprises a cam member 24 which extends between the legs 9, 11 of the handle 10 and is parallel to, but offset from, the pin 12. When the handle 10 pivots about the pin 12 the cam member 24 moves about the pin 12 in a circular path. When the handle 10 is in the closed position, as will be described in more detail with reference to FIGS. 2-4, the cam member 24 forms part of a structure which defines a channel for the strap which serves to prevent it from slipping during use.

A strap trapping member 26 is provided at a rear portion of the buckle body 4. The strap trapping member 26 is in the form of a plate which extends upwardly from the base 5 of the buckle body 4 and is angled towards the pin 12. The angle of the plate relative to the pin 12 will be described in more detail with reference to FIGS. 2-4. The function of the strap trapping member 26 is to define a channel for the strap in conjunction with the cam member 24 to prevent slippage of the strap during normal conditions of use. In particular, the strap trapping member 26 is intended to prevent or reduce slippage of the strap through the buckle 2 when it is subjected to repetitive high frequency (for example 1 Hz), low force cyclic loads, e.g. gust loads experienced in aviation.

The strap trapping member 26 is located towards the rear of the buckle body 4 such that when the handle 10 is moved into the closed position the cam member 24 moves into close proximity with the strap trapping member 26 (as shown in more detail in FIGS. 3 and 4). The strap trapping member 26 extends between the side walls 6,8 but is not attached directly to them. The strap trapping member 26 is only supported at one end and thus acts as a simple spring. When the handle 10 is locked in the closed position the distance between the strap trapping member 26 and the cam member 24 is approximately equal to, or slightly larger than, the thickness of a double layer of the untensioned strap, i.e. approximately 2-4 mm (a double layer of the strap will be trapped between the strap trapping member 26 and the cam member 24, as will be described in more detail in relation to FIG. 4). This ensures that the cam member 24 and the strap trapping member 26 define a channel for the strap which profiles the strap and prevents “ballooning”, such that the risk of slippage is prevented or at least greatly reduced. The distance between the strap trapping member 26 and the cam member 24 when the handle 10 is in the closed position is referred to as the width of the channel.

The strap trapping member 26 and/or the cam member 24 may have a roughened surface to increase friction between itself and the strap when the handle 10 is in the closed position. The surface of the strap trapping member 26 or cam member 24 may be knurled, toothed or provided with any other surface features which serve to increase friction between itself and the strap and prevent the strap from slipping.

The handle 10 and buckle body 4 are each provided with one of a pair of mating members 28. The mating members 28 are in the form of plates which are arranged such that when the handle 10 is moved from the open position to the closed position the mating members 28 come together to define a channel for a strap therebetween. A first one of the mating members 28 a is provided on the handle 10 and extends between the legs 9, 11 of the handle 10. A second one of the mating members 28 b is provided on the buckle body 4 and extends between the side walls 6, 8. When the handle 10 is locked in the closed position the distance between the mating members 28 is approximately equal to, or slightly larger than, the thickness of a double layer of a normal, untensioned strap, i.e. approximately 2-4 mm. This ensures that the strap is channeled between the mating members 28, which serves to prevent “ballooning” of the strap and reduce or prevent the risk of slippage. The distance between the mating members 28 when the handle 10 is in the closed position is referred to as the width of the channel.

Either one or both of the mating members 28 may have a roughened surface to increase friction between itself and the strap when the handle 10 is in the closed position. The surface of the mating member 28 may be knurled, toothed or provided with any other surface features which serve to increase friction between itself and the strap and prevent the strap from slipping.

Turning now to FIG. 2, this shows a plan view of the buckle 2 of FIG. 1 in the closed position. As can be seen, the spring biased latch 14 has been received in the recesses 20, 22 in the side walls 6, 8 to “lock” the handle 10 into the closed position. In order to move the handle 10 back to the open position, to release or adjust the buckle 2, it is necessary to apply a force to the spring biased latch sufficient to overcome the biasing force of the spring. The force is applied to a front position of the latch 14 a to release it from the recesses 20, 22. The force may conveniently be applied by grasping the handle 10 and latch 14 between thumb and forefinger and squeezing together.

FIG. 2 also shows the strap trapping member 26 and the cam member 24 and the relationship between them when the handle 10 is in the closed position. This relationship will be discussed in more detail with reference to FIGS. 3 and 4. Also shown in FIG. 2 is a first one of the mating members 28, which is the mating member 28 a provided on the handle 10. As the view in FIG. 2 is a plan view only the first mating member 28 a is visible as the mating members 28 come together when the handle 10 is in the closed position. The relationship between the mating members 28 will also be discussed in more detail with reference to FIGS. 3 and 4.

Turning now to FIGS. 3 and 4, these show a side sectional view of the buckle of FIGS. 1 and 2, taken along the line X-X in FIG. 2. The only difference between FIGS. 3 and 4 is that FIG. 3 is shown without a strap and FIG. 4 shows the buckle 2 with a strap 30 wound around the handle 10.

At the rear of the buckle body 4 (the left hand side of the buckle 2 as viewed in FIGS. 3 and 4) the strap trapping member 26 extends upwards relative to the base 5 of the buckle body 4. The strap trapping member 26 is angled towards the cam member 24 in order to improve the trapping mechanism. The angle of the strap trapping member 26 relative to the base 5 of the buckle body 4 is approximately 75□. In alternative embodiments of the buckle 2 the strap trapping member 26 may be orientated at right angles to the base 5 of the buckle body 4 or it may be orientated at a range of angles from 90□ to 45□ relative to the base 5 of the buckle body 4. It is even possible that the strap trapping member 26 may be angled away from the cam member 24, depending on the construction of the buckle 2. It will be clear to the person skilled in the art that the key feature of the strap trapping member 26 is its position relative to the cam member 24. In order to operate the strap trapping member 26 must be positioned such that it is in close proximity to the cam member 24 when the handle 10 is in the closed position. This ensures that the cam member 24 is able to define a channel between itself and the strap trapping member 26, which can restrict unwanted movement of the strap. When the handle 10 is in the closed position the distance between the strap trapping member 26 and the cam member 24 is known as the width of the channel.

Towards the front of the buckle body 4 (the right hand side as viewed in FIGS. 3 and 4) the mating members 28 come together to provide a further trap for a strap. As discussed above in relation to FIG. 1, a first mating member 28 a is provided on the handle 10 and a second mating member 28 b is provided on the buckle body 4. When the handle 10 is moved from the open position to the closed position the mating members 28 come together to define a channel between them. The distance between the mating members 28 when the handle 10 is in the closed position is known as the width of the channel.

Turning now to FIG. 4, this shows the same view of the buckle 2 as FIG. 3, with the further inclusion of a length of strap 30, which is indicated by a broken line. The strap 30 may conveniently be formed from any suitable material as is commonly used with conventional buckles. This may include, but is not limited to, textile webbing, for example polyester and polypropylene webbing.

With the handle 10 in the open position (as shown in FIG. 1) the strap 30 is fed in through an aperture 32 at the front of the buckle body 4, around the pin 12 and back out through the aperture 32 at the front of the buckle body 4. The free end of the strap 30 is then pulled tight to take up any slack in the strap 30. When it is desired to secure the strap 30 under tension the handle 10 is moved from the open position to the closed position, as described above. The handle 10 pivots about the pin 12 and the cam member 24, which is mounted on the handle 10, moves around the pin 12 in a clockwise direction (as indicated by the arrow A in FIG. 4). The cam member 24 moves in a direction towards the strap trapping member 26 and traps a portion of the strap 30 in a channel between itself and the strap trapping member 26. In addition to being held under tension by the cam member 24 the strap also passes through a channel defined by the cam member 24 and the strap trapping member 26 and is profiled by them. This serves to prevent, or at least reduce, the possibility of the strap 30 slipping under the high frequency, low force cyclic loads described above. The distance between the strap trapping member 26 and the cam member 24 when the handle 10 is in the closed position will be determined by the thickness of the strap 30 which the buckle 2 is designed to accommodate. In order to provide an adequate prevention or reduction of slippage the gap must be approximately the same width as, or slightly wider than, the thickness of a double layer of the strap 30. It is clear that the size of the gap will be dependent on the properties of the strap 30, but it will typically be in the region from 1-8 mm, more typically from 2-4 mm.

As discussed in relation to FIG. 3, the mating members 28, which are provided on the handle 10 and the buckle body 4, come together when the handle 10 is moved into the closed position to define a further channel for the strap 30. The gap between the mating members 28 in the closed position will be similar to the gap between the strap trapping member 26 and the cam member 24, i.e. it will be the same width as, or slightly wider than, the thickness of a double layer of the strap 30. As with the strap trapping member 26 and the cam member 24 the size of the gap will be dependent on the properties of the strap 30, but it will typically be in the region from 1-8 mm, more typically from 2-4 mm.

Although the embodiment of the buckle 2 described in relation to FIGS. 1-4 is provided with two strap trapping means it will be clear to the person skilled in the art that the buckle 2 could be provided with only one strap trapping means, i.e. either the strap trapping member 26 or the mating members 28, and it would still function satisfactorily. A particular advantage of the present invention is that both of the additional strap trapping means described are operated in the same action as the closing of the handle 10. This means that the buckle 2 can be utilised as a direct replacement for the currently available conventional buckles without the need to explain a new operating technique to the user. The user simply operates the buckle 2 in the conventional manner and this results in the strap trapping means engaging with the strap 30 to prevent, or reduce, slippage. 

1. A buckle comprising a buckle body with spaced apart side walls and a handle, the handle comprising a cam member and being pivotally mounted between the side walls such that it is movable between an open position, wherein a strap may be threaded upon the handle, and a closed position, wherein tension is applied to a strap threaded upon the handle, characterised in that the buckle further comprises strap trapping means arranged such that when the handle is in the closed position the strap trapping means defines a channel for the strap threaded upon the handle, to prevent or reduce slippage thereof.
 2. A buckle according to claim 1, wherein the buckle comprises more than one strap trapping means.
 3. A buckle according to claim 1, wherein, when the handle is in the closed position, the strap trapping means defines a channel for the strap which is the same width as, or slightly wider than, the thickness of the strap passing through the channel.
 4. A buckle according to claim 1, wherein the strap trapping means comprises a strap trapping member which is associated with the cam member, such that when the handle is moved from the open position to the closed position the cam member moves into close proximity with the strap trapping member.
 5. A buckle according to claim 4, wherein the strap trapping member comprises a plate.
 6. A buckle according to claim 5, wherein the plate extends upwardly from the base of the buckle.
 7. A buckle according to claim 5, wherein the plate is perpendicular to the side walls.
 8. A buckle according to claim 5, wherein the plate is angled towards the cam member.
 9. A buckle according to claim 1, wherein the strap trapping means comprises mating members, a first member being provided on the handle and a second member bring provided on the buckle body, the arrangement being such that when the handle is moved from the open position to the closed position the mating members come together to define the channel.
 10. A buckle according to claim 9, wherein the mating members are in the form of plates.
 11. A buckle according to claim 9, wherein the mating members define a channel which is the same width as, or slightly wider than, the thickness of the strap passing through the channel. 